1. Field of the Invention
The present invention relates to an adjustment device for adjusting wave shape of output of a DC-AC inverter, more particularly one, which will make the inverter provide a demanded stable fixed voltage output, preventing output voltage of the inverter from changing owing to the loading effect caused by electric appliances connected to the inverter, and which allows the inverter to be connected to an utility.
2. Brief Description of the Prior Art
DC-AC inverters are usually used in wide-open country and regions where there is access to the utility, which will convert the DC source of batteries in vehicles, boats, and planes into AC one for powering various electric appliances.
People are paying more and more attention to renewable sources of energy such as solar, wind and hydraulic energies owing to their understanding of the importance of environmental protection and the seriousness of energy crisis. Renewable sources of energy are in the form of direct current, which has to be converted into AC electricity by means of an inverter before it is used to power common electric appliances and equipments.
Referring to FIG. 9, a currently existing DC-AC inverter 5 includes a control device 51, a driving circuit 52, a DC-to-DC converter 53 connected to the driving circuit 52, a linking circuit 54 connected to the DC-to-DC converter 53, a driver 55 connected to the control device 51, a sine wave generator 56 connected to the driver 55, and a DC-to-AC converter 57 connected to both the sine wave generator 56 and the linking circuit 54. The control device 51 can be equipped with a digital circuit or microcontroller, and it is connected to the driving circuit 52. Therefore, direct current source will be sent to and boosted by the DC-to-DC converter 53, and the DC source with boosted voltage will be sent to the linking circuit 54. The DC-to-AC converter 57 will convert DC source into AC source, and the AC source will be sent to the linking circuit 54. The circuit of the inverter 5 is prone to burn if the duty cycle exceeds 50% at the front stage. And, the higher the duty cycle generated by the sine wave generator 56 is, the more the output voltage of the inverter 5 will be. Therefore, the output voltage of the inverter 5 is adjusted with the help of the sine wave generator 56, which will generate such a duty cycle wave shape that the duty cycle will be lower than 50% at the front stage.
Therefore, the DC-AC inverter can convert DC source into AC one for various common electric appliances. However, the output voltage of the inverter will drop owing to the loading effect caused by an electric appliance connected to the output terminals of the inverter, causing much inconvenience. Furthermore, the frequency of the output DC source of the inverter isn't necessarily equal to that of other DC-AC inverters. Consequently, the inverter can't be connected in parallel to another inverter or the utility grid, and there is room for improvement.